By Dan Breitwieser, TV 20 News.

Florida Highway Patrol troopers are still trying to figure out the cause of Sunday evening's two-car accident.

Tiffany Davis and her daughter Hunter, 10, are at Shands with injuries. But her son Owen, 3, and step-daughter Hailey, 10, didn't make it.

"Hailey was the greatest kid ever, she really was." says Hailey's aunt Karen Loock. "She was full of life and Owen was great. He was full of energy."

The crash is on about the only curve on County Road 225A between County Roads 326 and 329. Ribbons and wreaths already mark the spot.

FHP investigators say Tiffany Davis was driving a van north with the three kids when it hit a pickup truck driving south by James Roberts head-on.

"We don't think speed was an issue because the impact took place and all the vehicles came to rest right where the impact took place at," says Capt. Gregory Lamont with Florida Highway Patrol. "It was right after sunset, 5 minutes to 7, so it would have been dark."

A photographer took aerial pictures of the scene to help troopers get a better understanding of the curve. Troopers are still unsure which driver is at fault.

"If you look at the roadway in the daylight, there are no skid-marks," said Lamont. "So we have no idea who was traveling on which side of the road first, and how the vehicles traveled after the impact."

Troopers hope to have an answer in the next 60 days. But for the Davis family, there may not be an answer for why two kids who are described as lighting up the room, are no longer alive.

"Hailey, she used to bug me all the time," says Loock. "I loved it and I'm going to miss that the most."

Teachers, faculty and Hailey's 4th grade class at Idylwild Elementary School found out the news Monday afternoon.

Hunter Davis, 10, is listed in critical condition at Shands, while her mother Tiffany has improved to good condition. The driver of the truck, James Roberts, was treated at North Florida Regional Medical Center and was released.

Funeral arrangements have not been made yet for Hailey and Owen.